The invention relates to a process for the production of wear-resistant, coated surfaces. Processes of the type addressed here are known. They serve for example to provide a surface consisting of aluminum or an aluminum alloy, for example the surface of a hole, with an oxide layer. To carry out the prior-art coating process the workpiece is connected to the positive pole of a voltage source, therefore forming the anode. A lead plate connected to the negative pole forms the cathode which is introduced into the hole. An electrolyte, here diluted sulfuric acid, is conducted into the chamber bordered by the workpiece and the cathode. The chamber has an inlet and an outlet and the electrolyte flows through in one direction. It has been proven disadvantageous that the thickness of the aluminum oxide layer is different over the surface to be coated, that is, on one side of the workpiece the thickness of the oxide layer is greater than on the other side. Thereby desired tolerances in the form of the surface can be adhered to in all cases so that the coated surface must be reworked, for example, by grinding or honing in order to achieve a high precision in form and dimensions.
DE 1 909 870 describes a process for the galvanic deposition of metals on the outer and inner surfaces of porous metallic, or premetallized non-metallic, formed bodies. It was discovered that on the outer as well as on the inner metallic surfaces of a porous formed body a nearly uniform galvanic deposition of metal can be achieved if the electrolyte is pressed through the pores of the formed body serving as electrode at a certain rate, preferably at a rate of 80 to 130 cm/sec. If the formed body is very thick-walled, then a reduction of the layer thickness of the metal deposit in the direction of flow of the electrolyte is observed. By timed reversal of the direction of flow of the electrolytes and by arrangement of two anodes this disadvantage can be eliminated.